Vehicle electronic key system

ABSTRACT

A vehicle electronic key system includes a control device mounted on a vehicle and an electronic key for transmitting a response signal in response to reception of a request signal from the control device. The control device includes means for outputting a request signal to the electronic key in response to the ON operation of a main switch of the vehicle (request signal generation means, a transmission circuit, and a transmission antenna), means for detecting a response signal from the electronic key (a reception circuit and response signal matching means), and means for performing an alarm output (monitoring means, a third drive circuit, and an alarm lamp) when no response signal is detected in spite of the output of the request signal.

TECHNICAL FIELD

The present invention relates to an electronic key system for carryingout wireless communication between a transceiver (electronic key)carried by a user and a controller mounted on the vehicle, and, when anID is compared and there is a request from the normal user, starting theengine etc., the invention being suitable for use as, for example, anelectronic key system for a vehicle such as a motorcycle.

BACKGROUND ART

Japanese Laid-Open Patent Publication No. 2001-349110 and JapaneseLaid-Open Patent Publication No. 2001-349117 exist as electronic keysystems for a vehicle. The electronic key systems for a vehicledisclosed in these patent documents have activation means (switches)arranged in a door handle and trunk lid of the vehicle. If a useroperates (activates) these activation means, communication with theelectronic key commences, comparison is carried out between an IDtransmitted from the electronic key and an ID registered in thecontroller, and a door lock is released at a stage when a result isobtained that there is ID matching.

Also, in patent documents mentioned above, an activation means (aswitch) is also provided in an ignition knob, and after a user hasboarded a four-wheeled vehicle, communication with the electronic key iscarried out again, by operation of the ignition knob, and an IDcomparison is carried out in order to allow the engine to be started.Then, when results of the ID matching comparison have been obtained, theengine is started.

That is, with the electronic key system for a four-wheeled vehicle ofthe related art, the electronic key has functions for unlocking a doorand allowing starting of the engine.

An electronic key system that has a transmission antenna provided foreach door of a four-wheeled vehicle, which can release only the doorthat a portable device is closest to independently of the other doors ofthe vehicle, has also been proposed as related art (see, for example,Japanese Laid-Open Patent Publication No. 10-317754).

Also, as an electronic key system applied to a motorcycle, a system hasbeen proposed that is intended to achieve reliable theft prevention, bygenerating a random number based on a time taken from a power supply ofan immobilizer turning ON to starting of the engine (start time data),generating an authentication key and an authentication code by encodinginformation inherent to the key based on the random number, and carryingout authentication using the authentication key and the authenticationcode (see, for example, Japanese Laid-Open Patent Publication No.2001-12123).

Since the electronic key is carried by the user, there is a danger ofthe key being dropped inside the vehicle when the key is not in use. Inthe case of a four-wheeled vehicle, however, there is only a very lowpossibility of the electronic key being lost after use, even if it isdropped inside the vehicle.

However, when the electronic key system for a four-wheeled vehicle isapplied, as is, to a motorcycle, for example, if the electronic key isdropped by the user after starting the engine, there is not a problem ifit is noticed that the key has been dropped, however, if the motorcyclemoves without noticing that the key has been dropped, the key may becomelost and it will not be possible to restart the engine.

In the related art, in a system that has been applied to a motorcycle,theft prevention is a main consideration, and for example, afterboarding the vehicle once authentication of the normal user is complete,the security system is stopped. As a result, if the electronic key isdropped during travel, for instance, there is a danger that it will notbe detected.

Naturally, even with a four-wheeled vehicle, if the electronic key isdropped close to the door, the probability of the electronic keybecoming lost is high, and in this case also, it will not be possible torestart the engine.

The present invention has been conceived in view of these types ofproblems, and an object of the present invention is to provide anelectronic key system for a vehicle that can output a warning if a userdrops an electronic key while the vehicle is stopped or during travel,and that can reduce, to as low as possible, the probability of theelectronic key being lost when dropped by the user.

DISCLOSURE OF THE INVENTION

An electronic key system of the present invention has a controllermounted on the vehicle and a portable transceiver for transmitting anacknowledgement signal based on receipt of a request signal from thecontroller, the controller comprising first means for outputting arequest signal to the portable transceiver in response to an ONoperation of a start switch for the vehicle, second means for detectingan acknowledgement signal from the portable transceiver based on therequest signal, and third means for outputting a warning when theacknowledgement signal is not detected in the second means, regardlessof output of a request signal from the first means.

In this way, first of all a request signal is output from the firstmeans as a result of ON operation of a start switch for the vehicle bythe user. If the user is holding the portable transceiver, a requestsignal from the controller is received by the portable transceiver. Theportable transceiver transmits an acknowledgement signal based onreceipt of the request signal from the controller. The acknowledgementsignal output from the portable transceiver is detected by the secondmeans of the controller in the vehicle, and in that case, the engine isstarted without outputting a warning.

On the other hand, if the user is not holding the portable transceiver,or has dropped it and has not noticed, if the start switch is turned ONthen since the second means does not detect the acknowledgement signal,regardless of whether or not a request signal is output from the firstmeans, a warning is output through the third means and the user willnotice that they are not holding the portable transceiver.

In this way, with the present invention, during the step of starting thevehicle, even if the user has dropped the portable transceiver, it ispossible to make the user aware of this fact, and thus it is possible toreduce the probability of the portable transceiver becoming lost.

Also, another aspect of the electronic key system for a vehicle of thepresent invention, is that it includes a controller mounted on thevehicle, and a portable transceiver for transmitting an acknowledgementsignal based on receipt of a request signal from the controller, thecontroller comprising first means for outputting a request signal to theportable transceiver every fixed period of time, second means fordetecting an acknowledgement signal from the portable transceiver basedon the request signal, and third means for outputting a warning when theacknowledgement signal is not detected in the second means.

In this way, first of all a request signal is output every fixed periodof time through the first means. In the event that the user is holdingthe portable transceiver; an acknowledgement signal is output everyfixed period of time in response to the request signal from thecontroller. The acknowledgement signal output from the portabletransceiver is detected by the second means of the controller in thevehicle, and in this case, a warning is not output.

On the other hand, during travel of the vehicle, for example, in theevent that the user has dropped the portable transceiver, since anacknowledgement signal is not detected by the second means, this time awarning signal is output by the third means, and thus the user can bemade aware of the fact that the portable transceiver has been dropped.

In this way, with the present invention, in the event that the userdrops the portable transceiver during travel of the vehicle, this factcan be notified to the user and it is possible to reduce the probabilityof the portable transceiver becoming lost.

Another aspect of the electronic key system for a vehicle of the presentinvention is that it has a controller mounted on the vehicle and aportable transceiver for transmitting an acknowledgement signal based onreceipt of a request signal from the controller, the controllercomprising first means for outputting a request signal to the portabletransceiver every fixed period of time, second means for detecting anacknowledgement signal from the portable transceiver based on therequest signal, third means for outputting a warning when theacknowledgement signal is not detected in the second means, fourth meansfor outputting a request signal to the portable transceiver based on anON operation of a start switch for the vehicle, and fifth means foroutputting a warning when the acknowledgement signal is not detected inthe second means, regardless of output of a request signal from thefourth means.

In this way, even if the user drops the portable transceiver whenstarting the vehicle or during travel of the vehicle, it is possible tomake the user aware of that fact, and it is possible to make theprobability of losing the portable transceiver extremely small.

In the invention described above, the output period for the requestsignal from the first means can be from 10 to 100 seconds. If the outputperiod of the request signal is short, it is possible to improveprecision of checking whether or not the user is holding the portabletransceiver. However, a battery is provided in the portable transceiverand the acknowledgement signal is output using electrical power from thebattery. Therefore, as the period of the output signal becomes shorter,battery power is consumed and it will be necessary to replace thebattery sooner.

By making the output period of the request signal from 10 to 100seconds, it is possible to reduce battery consumption in the portabletransceiver, and to reduce the frequency with which the battery isreplaced.

Also, the third means can count the periods for which theacknowledgement signal is not detected, and output a warning at a pointin time when the count value becomes a specified value or greater. Sincethere will be cases when arrival of the acknowledgement signal at thesecond means is delayed, or the acknowledgement signal itself may bemissing due to effects of noise etc. during travel, it is possible toprevent frequent warning outputs by retaining a dead zone to a certainextent.

Also, in the invention described above, it is possible for thecontroller to further comprise sixth means for outputting a requestsignal to the portable transceiver based on activation of thecontroller, and seventh means for releasing a locked state of thevehicle when an acknowledgement signal from the portable transceiver isdetected in the second means based on the request signal from the sixthmeans.

If activation of the controller is carried out before turning the startswitch ON, it is possible to check whether or not the user is holdingthe portable transceiver in three situations, namely, when activatingthe controller, when turning the start switch ON, and during travel ofthe vehicle.

As a result, even if the electronic key system for a vehicle of thepresent invention is applied to a motorcycle, for example, in the eventthat the user drops the portable transceiver, that fact can be notifiedto the user and it is possible to make the probability of the portabletransceiver becoming lost extremely low.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural drawing showing an electronic key system of afirst embodiment;

FIG. 2 is a block drawing showing the structure of an electronic key;

FIG. 3 is a block diagram showing the structure of a controller;

FIG. 4A is a side elevation showing one example of a setting positionfor a transmission antenna on the vehicle, and FIG. 4B is a plan view ofthe same;

FIGS. 5A through 5F are timing charts showing normal processingoperations of the electronic key system of the embodiment;

FIGS. 6A through 6F are timing charts showing processing operations forthe case where it is detected that there is no electronic key at thetime of starting a vehicle, in the electronic key system of thisembodiment;

FIGS. 7A through 7F are timing charts showing processing operations forthe case where it is detected that there is no electronic key at thetime of starting a vehicle engine, in the electronic key system of thisembodiment; and

FIGS. 8A through 8F are timing charts showing processing operations forthe case where it is detected that there is no electronic key duringvehicle travel, in the electronic key system of this embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the electronic key system for a vehicle of the presentinvention applied to a system for a motorcycle (hereinafter, simplyreferred to as electronic key system embodiments) will now be describedwith reference to FIGS. 1 through 8F.

As shown in FIG. 1, an electronic key system 10 of this embodimentcomprises a portable transceiver 12 carried by a user, and a controller14 mounted on the vehicle. The portable transceiver 12 can be either akey type having an IC chip built-in or a card type having an IC chipbuilt in, however, in the case where a keyless system is adopted, thecard type is mainly used. In this embodiment, a description will begiven assuming that the portable transceiver 12 comprises a card type.Also, since the portable transceiver 12 is generally called anelectronic key, in the following description, the portable transceiverwill also be referred to as an electronic key.

The electronic key 12 is a card type, as described above, and as shownin FIG. 2, internally comprises a battery 20, a power supply circuit 22,a CPU 24, a receiving circuit 26 and a transmission circuit 28.

The power supply circuit 22 provides electrical power from the battery20 to the receiving circuit 26, transmission circuit 28 and CPU 24. Thereceiving circuit 26 has a receiving antenna, not shown, and receives arequest signal Sr or the like transmitted through the receiving antennafrom the controller 14, and extracts and demodulates it from a carrierwave. The demodulated signal is supplied to the CPU 24. The carrier wavefrequency of the request signal Sr is 100 kHz to 300 kHz.

The CPU 24 executes at least two computer programs (request signalcomparison means 30 and acknowledgement signal generating means 32). Therequest signal comparison means 30 compares whether or not a signalsupplied from the receiving circuit 26 is the request signal Sr, and ifit is the request signal Sr, transfers control to the acknowledgementsignal generating means 32. The acknowledgement signal generating means32 reads out ID data stored in a ROM, not shown, in response to arequest from the request signal comparison means 30, and adds anattribute representing acknowledgment to the ID data for output astransmission data Dt to the transmission circuit 28. The transmissioncircuit 28 has a transmission antenna, not shown, and performsmodulation of a carrier wave based on transmission data Dt supplied fromthe CPU 24, for transmission as an acknowledgement signal Sa through thetransmission antenna. The carrier frequency for the acknowledgementsignal Sa is 200 MHz to 500 MHz.

On the other hand, as shown in FIG. 3, the controller 14 mounted in thevehicle is constituted by a system LSI, for example, and comprises apower supply circuit 40, a CPU 42, a receiving circuit 44, atransmission circuit 46, an input circuit 48, an output circuit 50, afirst drive circuit 52 (actuator drive), a second drive circuit 54 (mainrelay drive), and a third drive circuit 56 (LED drive). Peripheral tothis controller 14, there are provided at least a battery 60, amain-switch 62, a handlebar actuator 64, a main relay 66, a warning lamp68 (LED), an activation switch 70 and a transmission antenna 72.

The main switch 62 has two fixed connection points 62 a and 62 b, andone movable connection point 62 c, with one fixed connection point 62 abeing connected to the battery 60, and the other fixed connection point62 b being connected to the input circuit 48 and the main relay 66.

As well as the other fixed connection point 62 b of the main switch 62,the activation switch 70 is also connected to the input circuit 48. Astarter switch 74 is connected to this input circuit 48, and operationis caused by an ON operation of the starter switch 74. In the followingdescription, description will mainly focus on the case where processingoperations are carried out based on operation of the main switch 62.

ON/OFF states of the activation switch 70 and ON/OFF states of the mainswitch 62 are supplied to the CPU 42 through the input circuit 48.

The power supply circuit 40 of the controller 14 supplies electricalpower from the battery 60 to the CPU 42, the receiving circuit 44, andthe transmission circuit 46, etc.

The receiving circuit 44 has a receiving antenna, not shown, and anacknowledgement signal Sa is received from the electronic key 12 throughthe receiving antenna, and extracted and demodulated from a carrierwave. The demodulated signal is supplied to the CPU 42.

The CPU 42 executes at least four programs (request signal generatingmeans 80, acknowledgement signal comparison means 82, monitoring means84 and peripheral instruction means 86).

The request signal generating means 80 reads out request data Dr (dataconstituting the source of the request signal Sr) from a ROM, not shown,in response to the ON operation of the activation switch 70 and ONoperation of the main switch 62, for output to the transmission circuit46. Also, after starting the engine, the request signal generating means80 reads out request data Dr from the ROM every fixed time and outputsthe data. The fixed time is set to between 10 and 1100 seconds, takinginto consideration consumption of the battery by the electronic key 12.

The transmission circuit 46 modulates a carrier wave based on therequest data Dr supplied from the CPU 42, and transmits, via thetransmission antenna 72, a request signal Sr.

As shown in FIG. 4A and FIG. 4B, the transmittable range of the requestsignal Sr is a spherical range (the range shown by circle A in FIG. 4Aand FIG. 4B) of a diameter of 1-1.5 m with the transmission antenna 72fitted to the vehicle 100 at the center, and is a narrow range comparedto the transmittable range of the acknowledgement signal Sa (a range ofa few m radius with the electronic key 12 as the center).

Therefore, as shown in FIG. 4A and FIG. 4B, if it is assumed that thevehicle 100 is, for example, a scooter provided with a space that canhold a helmet, not shown, below a seat 102, it is preferable to providethe transmission antenna 72 close to the center of the vehicle 100 sothat when the user boards the vehicle, opens the seat 102, or istraveling, etc., communication is reliably established with theelectronic key 12 carried by the user.

Here, when considering a linking line 108 of the center 104 a of thefront wheel 104 and the center 106 a of the rear wheel 106, the vicinityof the center of the vehicle 100 is a range from a point P1 that is ¼ ofthe line to a point P2 that is ¾ of the line, with the center 104 a ofthe front wheel 104 as a reference, for example. With this embodiment,the transmission antenna 72 is arranged close to the front of the seat102.

The acknowledgement signal comparison means 82 compares whether or not asignal supplied from the receiving circuit 44 is an acknowledgementsignal Sa, and if it is the acknowledgement signal Sa, it compareswhether or not ID data contained in the acknowledgement signal Samatches ID data stored in a memory, not shown.

The monitoring means 84 monitors presence or absence of arrival of anacknowledgement signal Sa (whether or not an ID match is detected by theacknowledgement signal comparison means 82) based on output of therequest signal Sr. The request signal generating means 80 awaits inputof the acknowledgement signal Sa from the point in time where requestdata Dr is output, and if an acknowledgement signal Sa does not arrivewithin a specified time (if an ID match is not detected by theacknowledgement signal comparison means 82), the count value isincremented by 1. At the point in time that the count value becomes aspecified value or greater, a warning signal Se is output to the thirddrive circuit 56.

In particular, if an acknowledgement signal Sa does not arrive within aspecified time from the point in time where request data Dr is outputbased on the ON operation of the activation switch 70 and the mainswitch 62, at that stage the warning signal Se is output to the thirddrive circuit 56.

Also, if an acknowledgement signal Sa does arrive within a specifiedtime from the point in time where request data Dr is output based on theON operation of the activation switch 70, the monitoring means 84activates the peripheral instruction means 86. The peripheralinstruction means 86 outputs a lock release signal to the first drivecircuit 52 in response to a request (lock release) from the monitoringmeans 84, outputs an enabling signal to the output circuit 50, and alsooutputs an ON signal to the second drive circuit 54.

The first drive circuit 52 drives an actuator 64 for the handlebar inresponse to input of the lock release signal from the CPU 42, andreleases a locked state of the handlebar 110 (refer to FIG. 4A and FIG.4B).

The output circuit 50 outputs an ignition/injection enabling signal toan ECU 110 (electronic control unit) in response to input of theenabling signal from the CPU 42. The ECU 110 determines fuel injectionamount and injection timing for the engine based on information fromvarious sensors, in response to input of the ignition/injection enablingsignal.

The second drive circuit 54 is put into an ON state based on input of anON signal from the CPU 42, and after that starts the engine and enters atravel possible state in a step where the main relay 66 is turned on byan ON operation of the main switch 62.

The third drive circuit 56 drives the warning lamp 68 in response toinput of the warning signal Se from the CPU 42, and the warning lamp 68emits light. It is possible to use an LED, for example, as the warninglamp 68.

If the main switch 62 is turned OFF, the main relay 66 becomes OFF, andthe engine is also stopped at the same time. If a locking operation isthen carried out, for example, putting the handlebar 110 in a lockedstate, the comparison operation for the acknowledgement signal Sa in thecontroller 14 is stopped, the ignition/injection enabling signal fromthe output circuit 50 is stopped, and the second drive circuit 54 isturned OFF.

Next, four representative processing operations of the electronic keysystem 10 of the first embodiment will be described with reference tothe timing charts of FIG. 5A to FIG. 8F. A request signal Sr is a signalhaving a pulse string based on request data Dr, and the acknowledgementsignal Sa is a signal having a pulse string based on data contained inID data, but in FIG. 5A to FIG. 8F, they have each been shown as singlepulse signals to simplify description.

First of all, normally, if the activation switch 70 is turned ON at timet1 in FIG. 5A with the user holding the electronic key 12, then as shownin FIG. 5C the request signal Sr is transmitted from the controller 14(refer to time t2) and communication with the electronic key 12commences.

When the user is in possession of the electronic key 12, the requestsignal Sr is received by means of the receiving circuit 26 of theelectronic key 12 (refer to FIG. 2). As shown in FIG. 5D, the electronickey 12 transmits an acknowledgement signal Sa in response to receipt ofthe request signal Sr (refer to time t3). The acknowledgement signal Sais supplied through the receiving circuit 44 of the controller 14 to theCPU 42 (refer to FIG. 3), and ID data included in the acknowledgementsignal Sa is compared. When it is judged that the ID data matches, thelocked state of the handlebar 110 is released (unlocked) by means of thecontroller 14 and the first drive circuit 52, as shown in FIG. 5E (referto time t4). At this time, the second drive circuit 54 is turned ON, andthe ignition/injection enabling signal is output from the output circuit50 of the controller 14 to the ECU 110.

Continuing on, at time t5 in FIG. 5B, if the main switch 62 is turned ONwith the user holding the electronic key 12, then as shown in FIG. 5Cthe request signal Sr is transmitted from the controller 14 (refer totime t6) and communication with the electronic key 12 is carried out.

When the user is carrying the electronic key 12, then in the same way asdescribed above, as shown in FIG. 5D, the electronic key 12 transmitsthe acknowledgement signal Sa in response to receipt of the requestsignal Sr (refer to time t7). The acknowledgement signal Sa is suppliedto the CPU 42 via the receiving circuit 44 of the controller 14, ID datacontained in the acknowledgement signal Sa is compared, and if it isjudged that ID data matches, then control transfers to the next step,namely a step where the request signal Sr is output every fixed time +τ.

From this stage, the vehicle 100 is traveling, and during this travelthe request signal Sr is output from the controller 14 every fixed timeτ. That is, communication with the electronic key 12 is carried outevery fixed time τ, and an acknowledgement signal Sa is output from theelectronic key 12 at substantially every fixed time τ.

Next, the processing operation when it has been detected that there isno electronic key 12 at the time the vehicle 100 is started will bedescribed with reference to FIGS. 6A through 6F.

First of all, at time t11 in FIG. 6A, if the activation switch 70 isturned ON while the user is not holding the electronic key 12, as shownin FIG. 6C, the request signal Sr is transmitted from the controller 14(refer to time t12), but in the controller 14 there is no receipt of anacknowledgement signal Sa corresponding to the output request signal Sr(refer to time t13 in FIG. 6D). As a result, the warning signal Se isoutput from the monitoring means 84 to the third drive circuit 56, andin this way, as shown in FIG. 6F, the warning lamp 68 is lit. Naturally,in this case, processing such as lock release for the handlebar 110 etc.is not carried out (refer to FIG. 6E).

The user notices that the electronic key 12 is not being carried becauseof the lighting of the warning lamp 68, and starting the engine whilenot holding the electronic key 12 can be avoided.

Next, a description will be given with, reference to FIGS. 7A through7F, of processing operations when the electronic key 12 has not beendetected at the time of starting the vehicle 100.

First of all, at time t21 in FIG. 7A, if the activation switch 70 isturned ON while the user is holding the electronic key 12, then as shownin FIG. 7C the request signal Sr is transmitted from the controller 14(refer to time t22), and communication with the electronic key 12commences.

When the user is in possession of the electronic key 12, the requestsignal Sr is received by means of the receiving circuit 26 of theelectronic key 12, and as shown in FIG. 7D, the electronic key 12transmits an acknowledgement signal Sa (refer to time t23). ID dataincluded in the acknowledgement signal Sa is compared in the controller14, and when it is judged that the ID data matches, the locked state ofthe handlebar 110 is released, as shown in FIG. 7E (refer to time t24).At this time, the second drive circuit 54 is turned ON, and theignition/injection enabling signal is output from the output circuit 50of the controller 14 to the ECU 110.

Continuing on, at time t25 in FIG. 7B, if the main switch 62 is turnedon without the user noticing that the electronic key 12 has beendropped, then as shown in FIG. 7C the request signal Sr is transmittedfrom the controller 14 (refer to time t26), and there is no receipt ofan acknowledgement signal Sa corresponding to the output request signalSr in the controller 14 (refer to time t27 in FIG. 7D). As a result, thewarning signal Se is output from the monitoring means 84 to the thirddrive circuit 56, and in this way the warning lamp 68 is lit, as shownin FIG. 7F.

The user is made aware of the fact that the electronic key 12 has beendropped by the lighting of the warning lamp 68, and it is possible toavoid the electronic key 12 becoming lost.

Next, a description will be given, with reference to FIGS. 8A through8F, of processing operations for the case where it is detected thatthere is no electronic key 12 during travel of the vehicle 100.

First of all, processing from switching on the activation switch 70 upto switching on the main switch 62 (processing from time t31 to timet37) is the same as the processing from time t1 to t7 in FIGS. 5Athrough 5F, and so description of this processing will be omitted.

If the engine is started in response to an ON operation of the mainswitch 62, control passes to a step for outputting the request signal Srevery fixed time τ, as described above. From this stage, the user istraveling on the vehicle 100, and during such travel, the request signalSr is output from the controller 14 every fixed time τ.

While traveling on the vehicle 100, if the electronic key 12 is dropped,for example, receipt of the acknowledgement signal Sa is not carried outby the controller 14 (refer to time t38 in FIG. 8D). When theacknowledgement signal Sa is not received by the monitoring means 84within a specified time from output of the request data Dr, the countvalue is incremented by 1. Then, in a process of sequentially outputtingthe request signal Sr, at time t39 when the count value becomes aspecified value or higher, a warning signal Se is output from themonitoring means 84 to the third drive circuit 56, and in this way thewarning lamp 68 is lit, as shown in FIG. 8F.

The user notices that the electronic key 12 has been dropped as a resultof the lighting of the warning lamp 68, and it is possible to avoid theelectronic key 12 becoming lost.

In this way, in the electronic key system 10 of this embodiment, in theevent that the user turns the activation switch 70 on while not holdingthe electronic key 12, since it will be detected that theacknowledgement signal Sa is not received in the receiving circuit 44,regardless of output of the request signal Sr from the controller 14, awarning is output via the monitoring means 84, and the user will noticethat they are not in possession of the electronic key 12.

If the user drops the electronic key 12 at the time of starting theengine, for example, since the acknowledgement signal Sa is not detectedin the receiving circuit 44, regardless of output of the request signalSr from the controller 14 in response to the main switch 62 being turnedon, a warning is output via the monitoring means 84 and the user willnotice that they have dropped the electronic key 12.

If the user drops the electronic key 12 during travel of the vehicle100, since the acknowledgement signal Sa is not detected in thereceiving circuit 44, regardless of output of the request signal Sr fromthe controller 14 at every fixed time τ, a warning is output via themonitoring means 84 and the user will notice that they have dropped theelectronic key 12.

In this way, it is possible to check whether or not the user is holdingthe electronic key 12 during at least three stages, namely when startingthe controller 14, when turning ON the main switch 62, and during travelof the vehicle 100.

As a result, even if the electronic key system 10 of this embodiment isapplied to a motorcycle, for example, in the event that the user dropsthe electronic key 12, that fact can be made known to the user and it ispossible to make the probability of losing the electronic key 12extremely low.

In particular, with the embodiment described above, the output period τfor the request signal Sr from the controller 14 is set at 10 to 100seconds. If the output period τ of the request signal Sr is made short,it is possible to improve precision of checking whether or not the useris in possession of the electronic key 12. However, a battery 20 isprovided in the electronic key 12 and the acknowledgement signal Sa isoutput using electrical power from the battery 20. Therefore, as theoutput period τ of the request signal Sr becomes shorter, batteryconsumption increases and the battery 20 must be replaced more often.

By setting the output period τ of the request signal Sr at 10 to 100seconds, it is possible to reduce consumption of the battery in theelectronic key 12, and it is possible to reduce the frequency with whichthe battery 20 needs to be replaced.

Also, with this embodiment, the periods in which the acknowledgementsignal Sa is not detected during travel of the vehicle 100, for example,are counted, and a warning is output when that count value is aspecified value or higher. Since there will be times when arrival of theacknowledgement signal Sa is delayed, or the acknowledgement signal Saitself is missing due to the effects of noise etc. during travel, it ispossible to prevent frequent warning output by causing a particulardead-zone to be held.

With the above-described example, lighting of a dedicated warning lamp68 has been given as an example of warning output, but it is alsopossible to output a warning sound using a dedicated buzzer.

Alternatively, it is possible to randomly light an indicator lamp insidean already existing meter, output a specified sound pattern by means ofthe horn, or cause a direction indicator to light up with a differentlighting pattern from normal.

However, since the horn and the direction indicator are safetycomponents, it is important not to operate them for the purpose ofwarning when starting the engine, and to use them as conventional safetycomponents.

The electronic key system for a vehicle of the present invention is notlimited to the above-described embodiments, and obviously variousstructures can be introduced without departing from the spirit and scopeof the invention.

1. An electronic key system for a vehicle, including a controllermounted on the vehicle and a portable transceiver for transmitting anacknowledgement signal based on receipt of a request signal from thecontroller, the controller comprising: first means for outputting arequest signal to the portable transceiver in response to an ONoperation of a start switch for the vehicle; second means for detectingan acknowledgement signal from the portable transceiver based on therequest signal; and third means for outputting a warning when theacknowledgement signal is not detected in the second means, regardlessof output of the request signal from the first means.
 2. The electronickey system for a vehicle according to claim 1, wherein the controllerfurther comprises fourth means for outputting a request signal to theportable transceiver based on activation of the controller, and fifthmeans for releasing a locked state of the vehicle when anacknowledgement signal from the portable transceiver is detected in thesecond means based on the request signal from the fourth means.
 3. Anelectronic key system for a vehicle, including a controller mounted onthe vehicle and a portable transceiver for transmitting anacknowledgement signal based on receipt of a request signal from thecontroller, the controller comprising: first means for outputting arequest signal to the portable transceiver every fixed period of time;second means for detecting an acknowledgement signal from the portabletransceiver based on the request signal; and third means for outputtinga warning when the acknowledgement signal is not detected in the secondmeans.
 4. The electronic key system for a vehicle according to claim 3,wherein an output period for the request signal of the first means is ina range from 10 to 100 seconds.
 5. The electronic key system for avehicle according to claim 3, wherein the third means counts periods inwhich the acknowledgement signal is not detected, and outputs a warningat a point in time when the count becomes greater than a specifiedvalue.
 6. The electronic key system for a vehicle according to claim 3,wherein the controller further comprises fourth means for outputting arequest signal to the portable transceiver based on activation of thecontroller, and fifth means for releasing a locked state of the vehiclewhen an acknowledgement signal from the portable transceiver is detectedin the second means based on the request signal from the fourth means.7. An electronic key system for a vehicle, including a controllermounted on the vehicle and a portable transceiver for transmitting anacknowledgement signal based on receipt of a request signal from thecontroller, the controller comprising: first means for outputting arequest signal to the portable transceiver every fixed period of time;second means for detecting an acknowledgement signal from the portabletransceiver based on the request signal; third means for outputting awarning when the acknowledgement signal is not detected in the secondmeans; fourth means for outputting a request signal to the portabletransceiver based on an ON operation of a start switch for the vehicle;and fifth means for outputting a warning when the acknowledgement signalis not detected in the second means, regardless of output of the requestsignal from the fourth means.
 8. The electronic key system for a vehicleaccording to claim 7, wherein an output period for the request signal ofthe first means is in a range from 10 to 100 seconds.
 9. The electronickey system for a vehicle according to claim 7, wherein the third meanscounts periods in which the acknowledgement signal is not detected, andoutputs a warning at a point in time when the count becomes greater thana specified value.
 10. The electronic key system for a vehicle accordingto claim 7, wherein the controller further comprises sixth means foroutputting a request signal to the portable transceiver based onactivation of the controller, and seventh means for releasing a lockedstate of the vehicle when an acknowledgement signal from the portabletransceiver is detected in the second means based on the request signalfrom the sixth means.